1. FIELD OF THE INVENTION
The invention relates to a method and apparatus for permanently locking a shiftable valve member, such as a flapper valve, in an open position in a well conduit.
2. HISTORY OF THE PRIOR ART
In the operation of modern oil and gas wells, it often becomes desirable to permanently lock in an open position a shiftable valve member, such as a flapper valve, which is disposed in a well conduit. This is particularly necessary when it is desired to perform various well servicing operations through the valve and it is not contemplated that the valve will again be employed in subsequent operation of the well. It has previously been disclosed that valves, including rotatable ball type valves, may be held in an open position by shifting a retainer mechanism into engagement with an operating sleeve for the valve to prevent the return of the operating sleeve and valve to a closed position. See, for example, U.S. Pat. No. 3,696,868 to Taylor, Jr. This requires incorporation in the valve actuating mechanism of the retainer mechanism and thus complicates the total cost of the shiftable valve when initially installed in the well. In many cases, this cost is unjustified because the occasion never arises for locking the shiftable valve in an open position. Furthermore, the lock open mechanism is continuously subjected to subsurface well conditions during normal operations, and may be damaged, corroded or stuck in the retracted position, preventing subsequent actuation when necessary.
It would be desirable, therefore, to provide a method and apparatus for effecting the retention of a shiftable valve member within a well conduit in an open position by a mechanism which is entirely separate from the valve mechanism and which can be subsequently inserted in the well conduit only when it becomes necessary to permanently lock the shiftable valve member in an open position.